The process of producing yarns from staple fibers such as cotton traditionally includes as an intermediate step, between the opening and cleaning of the staple fiber and the spinning and winding of the yarn, the formation of a loosely coalescent, bulky strand of fibers known as sliver. In sliver, the cotton fibers are generally aligned in lengthwise relation, but the sliver unit does not possess any twist or strength against separation of the fibers, even against its own weight.
As those skilled in the art of yarn making will recognize, the quality of the yarn relates directly to the quality of the sliver. For instance, sliver of a uniform thickness and density forms a uniform, consistently strong yarn, while a sliver that has bumps (extra-thick regions) or voids (thinner regions) will form in the first instance a yarn of inconsistent quality. While processes have been developed that enable such imperfections to be cut from a yarn during processing, this is an inefficient process, and it is therefore desirable to minimize imperfections in the sliver. During handling, sliver is particularly susceptible to the introduction of bumps and voids because of its lack of strength and resiliency.
For those reasons, the prevailing conventional view has been that the packaging of sliver is difficult and undesirable, both because of the additional handling and movement of the sliver that would be required, and because the traditional methods of handling sliver did not lend themselves to a packaging solution. However, this convention stands at odds with modern distributed manufacturing processes. In many cases, it is considered to be more efficient to specialize the functions of a processing plant, such that a portion of the yarn making process occurs in one plant, a second portion in another, and a third portion in yet another. However, if a particular function, such as the forming of sliver, is to be specialized into a plant, it is necessary for the sliver to be transported.
Traditionally, sliver is drawn from processed bulk cotton using a draw frame, a card, or a comb, and deposited in circular rows into a cylindrical sliver can made of plastic or another durable material. These sliver cans allow large volumes of sliver to be moved without excessively handling the sliver, but they are expensive and heavy. If the distance to be traversed is small, such as different buildings in a plant complex, then the sliver could be transported in sliver cans without great difficulty. However, if the distance to be traversed is large, such as would make use of over-the-road or overseas transport, then the weight and expense of the cans, the necessity of transporting empty cans, and the minimal density of uncompressed sliver make such transport imprudent and inefficient. Concerning the expense of transporting cotton, generally the determinative factor is not the weight of the material, but the bulk.
Conventional methods of compressing cotton fiber, such as baling, have proven impractical for sliver deposited in conventional cylindrical cans. The reason for this is that the conventional pattern of deposition of sliver into a cylindrical can—essentially concentric circular rows of sliver—does not result in a substantially uniform density of sliver. Specifically, the density of sliver in the center of the can is higher than the density of sliver near the edge. If sliver in a cylindrical can is compressed to its maximum practical density at the center of the can, then the sliver at the edge is insufficiently compressed to allow the resulting compressed package to be handled. Such compression does not result in a stable package. Compression of the sliver has heretofore been thought to be impractical.
Consequently, the usual practice is to conduct substantially all of the steps by which staple fiber is processed into yarn in the same location. This is, however, an inflexible, capital-intensive, and inefficient arrangement in many cases, because of a desire on the part of yarn makers to conduct some operations, such as cleaning and carding, near the cotton gin (and therefore near the cotton fields), but other operations, such as spinning, in an area where labor or equipment costs might be lower.
What is needed is a system for and a method of packaging sliver in a manner that preserves the physical integrity of the sliver while permitting efficient transport in a compressed state, without requiring transport to be made in a sliver can.